This invention relates to mounting means for high frequency vibration members and, more specifically, refers to mounting means for solid resonators, also known as mechanical impedance transformers, sonotrodes, horns, tools, concentrators, couplers and the like, used for coupling high frequency vibrations in the sonic or ultrasonic frequency range to a workpiece. The vibrations are used for joining thermoplastic parts, welding metal parts, abrasive slurry machining of glass or ceramic workpieces and the like. The construction and use of these vibration members is well known and fully described in "Ultrasonic Engineering" (book) by Julian R. Frederick, John Wiley & Sons, New York, N.Y. (1965), pp. 89-103.
The mounting means for a vibration member must be designed to substantially decouple the vibrations of the vibration member, which, when operative, is resonant as a one-half wavelength resonator for high frequency vibrations of predetermined frequency traveling longitudinally therethrough, from the mounting means without impairing the operation of the vibration member. Absent such decoupling, there is a loss of vibratory energy and the transmission of vibrations to mounting means and to other parts of a machine where the existence of vibrations is highly undesirable.
Mounting the vibration member to a stationary support is effected most commonly by providing support means which engage the vibration member at a nodal region or an antinodal region present in the vibration member when the high frequency vibrations are transmitted through the member along its longitudinal axis from a radially disposed input surface at one end to a radially disposed output surface at the other end. Under those conditions and assuming a one-half wavelength resonator, there exists an antinodal region of the vibrations at the input surface and at the output surface, and a nodal region of the vibrations will be present at a region medially between the antinodal regions, the precise location of the nodal region being dependent on the mechanical configuration of the resonator. At the nodal region the vibrations appear as substantially radially directed vibrations.
Mounting means using flexible metallic elements engaging a vibration member at antinodal regions of the vibrations have been disclosed, for instance, in U.S. Pat. No. 3,752,380 entitled "Vibratory Welding Apparatus" issued to A. Shoh, dated Aug. 14, 1973. The disadvantage of that arrangement resides in the fact that the vibration member must be at least one full wavelength long.
Other mounting means coupled to a vibration member are shown in U.S. Pat. Nos. 2,891,178, 2,891,179 and 2,891,180 entitled "Support for Vibratory Devices", issued to W. C. Elmore, dated Jun. 16, 1959. These patents disclose various decoupling means engaging the vibration member at an antinodal region. The decoupling means comprise tuned elements one-quarter or one-half wavelength long. These mounts, because of their complexity and space requirements, have not found wide acceptance and are rarely present in commercial apparatus.
As a result of the above stated shortcomings, several mounts have been developed which support the vibration member at its nodal region. One current design, in wide use, provides the vibration member with a thin flange which protrudes radially from the nodal region of the vibration member. Elastomer "O"-rings are disposed on either side of the flange, all enclosed in a two-piece metallic annular ring, see U.S. Pat. No. 4,647,336 issued to J. D. Coener et al, dated Mar. 3, 1987. The elastomer "O"-rings serve to dampen the vibrations present at the nodal region of the vibration member with respect to the annular ring, which, in turn, is held stationary in a housing. However, this construction, although widely used, has several inherent problems. The "O"-rings are subject to wear and the elastic rings fail to provide the desired degree of rigidity for the vibration member in precision applications, specifically, the vibration member is subject to movement responsive to an axial or lateral force.
In order to overcome the above stated problem, metallic nodal mounts have been developed which provide greater rigidity. However, the designs now in use exhibit significant disadvantages in one design, the vibration member and the metallic decoupling flange are made from a single piece of material, requiring intricate and expensive machining operations. Another design uses a single "L"-shaped decoupling flange which also is machined from bar stock and occupies a rather large amount of space.